javascript - can't get the key of a datasnapshot - Stack Overflow

admin管理员组

文章数量:1391947

I am trying to get the key of a snapshot with the

dataSnapshot.key()

method, but it doesn't seem to be working. Here is the related code:

index.html:

...

<select id="resList" size="20"></select>

...

index.js:

function addChild(name, id) {
    var list = document.getElementById("resList");
    var item = document.createElement("option");
    item.text = "Resolution " + id + ": " + name;
    list.add(item);
}

function changeChild(name, index) {
    var list = document.getElementById("resList");
    var item = document.createElement("option");
    item.text = "Resolution " + (index+1) + ": " + name;

    list.remove(index);
    list.add(item, index);
}

function removeChild(index) {
    var list = document.getElementById("resList");
    list.remove(index);
}

function init() {
    const resolutionRef = firebase.database().ref().child('resolutions');

    resolutionRef.on('child_added', function(childSnapshot, prevChildKey) {
        if (prevChildKey == null)
            prevChildKey = "0";

        addChild(childSnapshot.val(), parseInt(prevChildKey) + 1);
    });

    resolutionRef.on('child_changed', function(childSnapshot, prevChildKey) {
        if (prevChildKey == null)
            prevChildKey = "0";

        changeChild(childSnapshot.val(), parseInt(prevChildKey));
    });

    resolutionRef.on('child_removed', function(oldChildSnapshot) {
        removeChild(parseInt(oldChildSnapshot.key()));
    });
}

window.onload = init;

I have a child of the 'root' reference called 'resolutions'. For each resolution a new child to the 'resolutions' reference is created. Each resolution has a name and an ID. I'm storing the ID of each resolution as the key and it's name as the value. This is convenient because this way I can determine the index of a resolution in 'resList' by simply subtracting one of it's key.

The above code works fine for adding and changing children, but for some reason when I remove a child nothing happens.

Thanks for any help in advance!

I am trying to get the key of a snapshot with the

dataSnapshot.key()

method, but it doesn't seem to be working. Here is the related code:

index.html:

...

<select id="resList" size="20"></select>

...

index.js:

function addChild(name, id) {
    var list = document.getElementById("resList");
    var item = document.createElement("option");
    item.text = "Resolution " + id + ": " + name;
    list.add(item);
}

function changeChild(name, index) {
    var list = document.getElementById("resList");
    var item = document.createElement("option");
    item.text = "Resolution " + (index+1) + ": " + name;

    list.remove(index);
    list.add(item, index);
}

function removeChild(index) {
    var list = document.getElementById("resList");
    list.remove(index);
}

function init() {
    const resolutionRef = firebase.database().ref().child('resolutions');

    resolutionRef.on('child_added', function(childSnapshot, prevChildKey) {
        if (prevChildKey == null)
            prevChildKey = "0";

        addChild(childSnapshot.val(), parseInt(prevChildKey) + 1);
    });

    resolutionRef.on('child_changed', function(childSnapshot, prevChildKey) {
        if (prevChildKey == null)
            prevChildKey = "0";

        changeChild(childSnapshot.val(), parseInt(prevChildKey));
    });

    resolutionRef.on('child_removed', function(oldChildSnapshot) {
        removeChild(parseInt(oldChildSnapshot.key()));
    });
}

window.onload = init;

I have a child of the 'root' reference called 'resolutions'. For each resolution a new child to the 'resolutions' reference is created. Each resolution has a name and an ID. I'm storing the ID of each resolution as the key and it's name as the value. This is convenient because this way I can determine the index of a resolution in 'resList' by simply subtracting one of it's key.

The above code works fine for adding and changing children, but for some reason when I remove a child nothing happens.

Thanks for any help in advance!

• javascript
• web
• firebase
• firebase-realtime-database

Share Improve this question Follow edited Aug 22, 2016 at 4:24 Frank van Puffelen 601k8585 gold badges890890 silver badges860860 bronze badges asked Aug 21, 2016 at 16:35 zomnombomzomnombom 99422 gold badges99 silver badges1515 bronze badges 2

• 3 What version of the Firebase JavaScript SDK are you using? In 2.x snapshot.key() was a function. In 3.x it changed to a read-only property, so would the equivalent became snapshot.key. – Frank van Puffelen Commented Aug 21, 2016 at 21:04
• @FrankVanPuffelen It works! Thanks! (I am using firebase 3.3.0 by the way) – zomnombom Commented Aug 22, 2016 at 4:24

Add a ment  | 

1 Answer 1

Sorted by: Reset to default 8

As @FrankVanPuffelen suggested, it seems 'key' is no longer a function, but rather a variable. So

var key = dataSnapshot.key;

does work, but

var key = dataSnapshot.key();

doesn't.

本文标签： javascriptcan39t get the key of a datasnapshotStack Overflow